Ethanol exposure affects gene expression in the embryonic organizer and reduces retinoic acid levels

Department of Cellular Biochemistry and Human Genetics, Faculty of Medicine, Hebrew University, POB 12272, Jerusalem 91120, Israel.
Developmental Biology (Impact Factor: 3.55). 04/2005; 279(1):193-204. DOI: 10.1016/j.ydbio.2004.12.014
Source: PubMed


Fetal Alcohol Spectrum Disorder (FASD) is a set of developmental malformations caused by alcohol consumption during pregnancy. Fetal Alcohol Syndrome (FAS), the strongest manifestation of FASD, results in short stature, microcephally and facial dysmorphogenesis including microphthalmia. Using Xenopus embryos as a model developmental system, we show that ethanol exposure recapitulates many aspects of FAS, including a shortened rostro-caudal axis, microcephally and microphthalmia. Temporal analysis revealed that Xenopus embryos are most sensitive to ethanol exposure between late blastula and early/mid gastrula stages. This window of sensitivity overlaps with the formation and early function of the embryonic organizer, Spemann's organizer. Molecular analysis revealed that ethanol exposure of embryos induces changes in the domains and levels of organizer-specific gene expression, identifying Spemann's organizer as an early target of ethanol. Ethanol also induces a defect in convergent extension movements that delays gastrulation movements and may affect the overall length. We show that mechanistically, ethanol is antagonistic to retinol (Vitamin A) and retinal conversion to retinoic acid, and that the organizer is active in retinoic acid signaling during early gastrulation. The model suggests that FASD is induced in part by an ethanol-dependent reduction in retinoic acid levels that are necessary for the normal function of Spemann's organizer.

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Available from: Graciela Pillemer-Amdur, Jun 28, 2014
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    • "EtOH-treated zebrafish embryos revealed that the GSC-positive cells remain at the dorsal blastopore lip, whereas in untreated embryos, these cells have already invaginated and moved rostrally (Blader and Strahle, 1998). It has also been suggested that increased GSC expression in EtOH-treated embryos was dependent on RA signaling in Spemann's organizer, and this might be one of its earliest effects as a teratogen (Yelin et al., 2005 "
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    ABSTRACT: Fetal alcohol spectrum disorder (FASD) is a set of developmental malformations caused by excess alcohol consumption during pregnancy. Using an in vitro system, we examined the role that chronic ethanol (EtOH) exposure plays in gene expression changes during the early stage of embryonic differentiation. We demonstrated that EtOH affected the cell morphology, cell cycle progression and also delayed the down-regulation of OCT4 and NANOG during differentiation. Gene expression profiling and pathway analysis demonstrated that EtOH deregulates many genes and pathways that are involved in early embryogenesis. Follow-up analyzes revealed that EtOH exposure to embryoid bodies (EBs) induced the expression of an organizer-specific gene, goosecoid (GSC), in comparison to controls. Moreover, EtOH treatment altered several important genes that are involved in embryonic structure formation, nervous system development, and placental and embryonic vascularization, which are all common processes that FASD can disrupt. Specifically, EtOH treatment let to a reduction in ALDOC, ENO2 and CDH1 expression, whereas EtOH treatment induced the expression of PTCH1, EGLN1, VEGFA and DEC2 in treated EBs. We also found that folic acid (FA) treatment was able to correct the expression of the majority of genes deregulated by EtOH exposure during early embryo development. Finally, the present study identified a gene set including GSC, which was deregulated by EtOH exposure that may contribute to the etiology of fetal alcohol syndrome (FAS). We also reported that EtOH-induced GSC expression is mediated by Nodal signaling, which may provide a new avenue for analyzing the molecular mechanisms behind EtOH teratogenicity in FASD individuals. Copyright © 2013 John Wiley & Sons, Ltd.
    Full-text · Article · Mar 2014 · Journal of Applied Toxicology
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    • "In vertebrates, gastrulation developmental events establish the body axes (Solnica-Krezel and Sepich, 2012). Ethanol was previously shown to disrupt gastrulation cell movements (Blader and Strähle, 1998; Yelin et al., 2005; Zhang et al., 2010). Our experiments establish that abnormal epiboly and gastrulation cell movements are associated with yolk cell microtubule cytoskeleton, radial intercalation cell movement, shield blastomere cell movement, blastomere cell adhesion and, specifically, pcdh18a expression defects. "
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    ABSTRACT: Fetal alcohol spectrum disorder (FASD) occurs when pregnant mothers consume alcohol, causing embryonic ethanol exposure and characteristic birth defects that include craniofacial, neural and cardiac defects. Gastrulation is a particularly sensitive developmental stage for teratogen exposure, and zebrafish is an outstanding model to study gastrulation and FASD. Epiboly (spreading blastomere cells over the yolk cell), prechordal plate migration and convergence/extension cell movements are sensitive to early ethanol exposure. Here, experiments are presented that characterize mechanisms of ethanol toxicity on epiboly and gastrulation. Epiboly mechanisms include blastomere radial intercalation cell movements and yolk cell microtubule cytoskeleton pulling the embryo to the vegetal pole. Both of these processes were disrupted by ethanol exposure. Ethanol effects on cell migration also indicated that cell adhesion was affected, which was confirmed by cell aggregation assays. E-cadherin cell adhesion molecule expression was not affected by ethanol exposure, but E-cadherin distribution, which controls epiboly and gastrulation, was changed. E-cadherin was redistributed into cytoplasmic aggregates in blastomeres and dramatically redistributed in the extraembryonic yolk cell. Gene expression microarray analysis was used to identify potential causative factors for early development defects, and expression of the cell adhesion molecule protocadherin-18a (pcdh18a), which controls epiboly, was significantly reduced in ethanol exposed embryos. Injecting pcdh18a synthetic mRNA in ethanol treated embryos partially rescued epiboly cell movements, including enveloping layer cell shape changes. Together, data show that epiboly and gastrulation defects induced by ethanol are multifactorial, and include yolk cell (extraembryonic tissue) microtubule cytoskeleton disruption and blastomere adhesion defects, in part caused by reduced pcdh18a expression.
    Full-text · Article · Oct 2013 · Biology Open
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    • "Johnson et al. [91] demonstrated in an in vivo experiment on mouse that the excessive cell death induced by Eth in limb buds was prevented by RA supplementation. In experiments carried out on Zebra fish embryos, Eth (100 mM) induced very severe malformations that were rescued by cotreatment with RA 10 −9 M. Similar results were obtained by Yelin et al. [92] on Xenopus embryos. On the other hand, chemicals able to inhibit CYP26 enzymes may be responsible of increased concentrations of RA. "
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    ABSTRACT: Biomarkers of effect are measurable biochemical, physiological or other alterations within an organism that can be recognized as causing an established or potential impairment of embryo-fetal development. They may be identified studying the mechanisms of action of teratogens. Hyperacetylation of histones, oxidative stress, cholesterol and retinoic acid unbalance are some of the identified mechanisms of action of some known teratogens. Nevertheless, their use is not currently applicable in human pregnancy because of the difficulty of the choice of biological material, the time when the material must be obtained, and the invasivity of methods. Furthermore, before using them in human pregnancy studies, biomarkers should be validated in experimental animals and in epidemiologic studies. On the contrary, some biomarkers could be useful in the screening of developmental toxicity of chemicals and drugs, comparing molecules of the same chemical class or with the similar pharmacologic activity, and using adequate in vitro tests, in order to reduce the use of experimental animals.
    Full-text · Article · May 2012 · Reproductive Toxicology
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